1. Field of the Invention
The present invention relates to a secondary arc extinction device in a multi-conductor transmission line electric power system in which an electrostatic coupling between the lines is strong and problems are thereby caused.
2. Description of the Prior Art
The above-noted problems are that the arc generated by back flashover at the installation of the insulator for the transmission line (which is hereinafter referred to as "secondary arc") is not extinguished to disable the reclosing at a high speed or it is impossible to take a sufficient non-voltage period of time by the fact that the induction electric current or the induction voltage is supplied from the whole phase or the whole line due to the electrostatic coupling even after the circuit breakers at both ends of the transmission line are interrupted when there is caused a short circuit due to the damage caused by lightning or the like at the insulator installation.
Nextly described with the aid of FIGS. 1, 2a, 2b, 3 and 4 is the conventional electric power transmission line system. Specifically, a power transmission line (R, S & T phases) is considered wherein the fixed reactor with zero phase, i.e., the reactor between the neutral point of the star-connection and ground, compensation is provided as shown in FIG. 1. In FIG. 1,
Y.sub.ca : power transmission line a phase ground admittance, PA1 Y.sub.cb : power transmission line b phase ground admittance, PA1 Y.sub.cc : power transmission line c phase ground admittance, PA1 Y.sub.cab : power transmission line a-b phase interphase admittance PA1 Y.sub.cbc : power transmission line b-c phase interphase admittance PA1 Y.sub.cca : power transmission line c-a phase interphase admittance PA1 Y.sub.La : 1/.omega..multidot.La: reactor a phase admittance, PA1 Y.sub.Lb : 1/.omega..multidot.Lb: reactor b phase admittance, PA1 Y.sub.Lc : 1/.omega..multidot.Lc: reactor c phase admittance, PA1 Y.sub.g : 1/.omega..multidot.Lg: neutral point reactor admittance, PA1 L.sub.a : reactor a phase reactance, PA1 L.sub.b : reactor b phase reactance, PA1 L.sub.c : reactor c phase reactance, PA1 L.sub.g : neutral point reactor reactance,
In addition, the reactor with zero phase compensation which is shown in FIG. 2(a) can be resolved into components between lines, as well as ground components as shown in FIG. 2(b). In FIG. 2(b), if it is assumed that m=Y.sub.La +Y.sub.Lb +Y.sub.Lc +Y.sub.g, each admittance will be obtained as the following: EQU Y.sub.Lab =Y.sub.La .multidot.Y.sub.Lb /m EQU Y.sub.Lbc =Y.sub.Lb .multidot.Y.sub.Lc /m EQU Y.sub.Lca =Y.sub.Lc .multidot.Y.sub.La /m EQU Y.sub.ag =Y.sub.a .multidot.Y.sub.g /m EQU Y.sub.bg =Y.sub.b .multidot.Y.sub.g /m EQU Y.sub.cg =Y.sub.c .multidot.Y.sub.g /m
On the other hand, as shown in FIG. 3, there is considered a state in which the a phase circuit breaker CB is opened after an a phase ground short-circuit problem has occurred. Then, an induced electric current i.sub.a flows into the problem point A from the healthy phases b and c by way of Y.sub.cab and Y.sub.cca. In addition, the condition of the recovery voltage v.sub.r and the secondary arc current i.sub.a for the continuation of the secondary arc is dependent upon the weather conditions, the primary arc current, the time, the design of the insulator of the line, etc. In other words, it becomes possible to extinguish the secondary arc if it becomes possible to limit the secondary arc current and the recovery voltage in a range in which either the recovery voltage v.sub.r or the secondary arc current i.sub.a is small.
Similarly, the induction via the power transmission line phase ground admittances Y.sub.caa' Y.sub.cab' and Y.sub.cac' from the healthy transmission line is received in the case of a juxtaposed pair of transmission lines as shown in FIG. 4, but it is difficult to compensate for the capacitance between the lines with the reactor which is constituted as shown in FIG. 1.